Aromatic Lithiation Directed by the Carboxylic Acid Groups. Synthesis of 9-Substituted Dibenzodioxin-1-carboxylic Acids and 6-Substituted Phenoxathiin-4-carboxylic Acids

Article abstract of DOI:10.1021/jo00289a012

An efficient procedure has been developed for the regiospecific synthesis of 9-substituted dibenzo<1,4>dioxin-1-carboxylic acid derivatives.Lithiation of dibenzo<1,4>dioxin-1-carboxylic acid forms the lithium carboxylate, which directs subsequent metalation exclusively to the 9-position.Conditions for the controlled mono- and dilithiation of dibenzo<1,4>dioxin itself, leading to the direct synthesis of the corresponding mono- and isomeric dimethyl esters, are also described.